The present invention relates to a leveling system for a vehicle, and more particularly to a height control valve for use with such a leveling system.
Many vehicles include leveling systems that automatically adjust the suspension of the vehicle to compensate for various loads. These systems are installed in various vehicles, ranging from passenger cars to semi-trucks and semi-trailers. A conventional leveling system includes pneumatic suspension elements, such as shocks or air springs, that can be inflated or deflated to control the height of the frame with respect to the axle. For example, with semi-trailers, heavy loads can cause the suspension to sag, thereby decreasing the distance between the frame and the axle. Further, if the load is not evenly distributed throughout the trailer, the load may also alter the attitude of the trailer, for example, the fore-aft tilt and/or side-to-side tilt. These conditions can adversely affect the handling of the trailer, and can even result in damage to the suspension, frame and axle. With conventional leveling systems, this problem is addressed by inflating the pneumatic suspension to compensate for the load. Specifically, when the attitude of the trailer has been affected by an uneven load, the various suspension elements can be inflated or deflated independently to return the trailer to the desired attitude.
In many leveling systems, the height of the suspension is automatically controlled by mechanical height control valves. Mechanical height control valves usually are located between a source of compressed air and the suspension elements. When the distance between the axle and frame falls below the desired position, the height control valve automatically causes inflation of the suspension, and when the distance between the axle and the frame is too great, the height control valve automatically causes the suspension to exhaust.
An example of a mechanical height control valve is shown in U.S. Pat. No. 5,860,450 to Trudeau. Conventional mechanical height controls such as this include a valve body and a control arm. The valve body usually is mounted directly to a vehicle frame and houses a valve assembly which controls the flow of air through the valve to the suspension elements. The control arm extends from the valve body to the axle and is mechanically connected to the valve assembly within the valve body by an actuator mechanism. The control arm is capable of moving the valve between different positions mechanically via a purely mechanical connection. When the orientation of the axle relative to the frame changes, the control arm moves, thus mechanically reconfiguring the valve body, which in turn inflates or deflates the appropriate air spring to level the vehicle.
Although such conventional mechanical height control valves operate relatively well, there is room for improvement with their operation. For example, the mechanical connection between the control arm and the valve assembly of a mechanical height control valve wears over time. With this wear, the sensitivity and exact positioning of the valve, and thus the precise inflation or deflation of the suspension, is compromised. In addition, the tolerances between the control arm and the valve assembly can deteriorate with such wear, or simply from improper adjustment. Accordingly, the valve assembly may not move as far as it did when it was new or first configured. In turn, the mechanical ride height control valve may not timely inflate or deflate enough air from the suspension. Alternatively, the mechanical connection between the actuator and the valve assembly may become so worn that it cannot properly control the valve assembly, and therefore the height leveling ability of the height control valve becomes significantly diminished. As a result, the vehicle is not properly leveled, and this condition can have adverse affects on vehicle stability and fuel consumption.